06 February 2011

Wisdom of the crowd

The term wisdom of the crowd has been popularized by Surowiecki in his 2004 book of the same name. Crowds, he argues, are better than a single entity at processing information, coordinating (eg optimizing pavement flow) and cooperating (local networks of trust). Four criteria for a crowd to be wise are:

  • diversity of opinion
  • independence
  • decentralization/localization
  • aggregation, ie combining private thoughts into collective decisions

Surowiecki's book deals with our society, economics and sociology. The wisdom of the crowd paradigm can also be applied to various domains of computer science.

Domain Example What it's not about
Machine Learning State-of-the-art classifiers are boosted random forests. Build many decision trees taking random features and a random part of the whole data set (bootstrapping). In the end, aggregate all of them (bagging). It's not about having a complex and smart model, it's about having millions of "slightly better than random" trees combined together, reducing the variance of the model.
Information Retrieval Google uses MapReduce for data processing. Separate your algorithm in small elementary treatments so that it can scale. The more hardware, the faster. It's not about having a smart and complex algorithm that needs to have 64G of RAM, it's about having many second-hand machines doing an elementary job in a pipelined process, reducing the reliability on a particular machine.

In the case of MMOG, the dominant paradigm is a tightly-coupled client-server architecture. And although server hardware scales, it's still rudimentary: the cutting in shards is often done manually and there's rarely a dynamic allocation of ressources to a particular world region (although that would be helpful in WoW in case of gnome warrior demonstrations). The coupling between client and server has a lot of limits. There are ways to prevent cheating in peer-to-peer MMOG architectures, so why is peer-to-peer still considered a joke?

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